Roller cone bits have typically used roller bearings and have employed a variety of connection methods for the cone to the bit body. U.S. Pat. No. 2,038,388 used a pin 19 that turned on bearings 18 with the cone 1. A set screw into the pin 19 through the cone 1 ensured that the pin and cone would turn together. The bearings 18 get preloaded but not the roller bearings between the head and the cone. U.S. Pat. No. 2,490,151 shows a tension rod mounted to cone, then welded to the head. It retains the cone but does not use rollers, eliminate axial play, communicate grease, or load the bearing assembly. It also acts as a thrust pin. U.S. Pat. No. 3,193,025 uses threads in the nose of the head bearing to lock down a flanged head and load the opposed tapered rollers. In US Publication 2009/0173546 the entire head bearing is independent of the head section itself, and is used as both the male journal as well as the pre-loading mechanism. There is no provision for grease compensation.
What is needed is a way of taking out axial play from bearings on a roller cone while still providing for a sufficiently strong support structure adjacent the nose bearing to withstand the loads encountered during drilling or reaming. The present invention applies tension to a tension rod in the head at a remote location from the head end where the cone nose bearing is supported. Grease passages are provided from a fill location in the rear of the head through the bore for the tension rod and on the way to the cone bearings. The rod is provided with a flat to minimize material removal as an aid to resisting bending stresses through the cone and to allow a more sturdy support for the bearing assembly. An alignment feature is provided to allow the flat to be oriented to the grease passages and to allow torque to be applied to a torque nut whose position is then maintained with welding. The nose bearing can be supported from a retainer nut threaded into the cone such that tension in the rod will remove the axial play on the nose bearing against the retainer nut and further tension will bring the head and cone closer to remove axial play on the main bearing. Alternatively a spacer between the bearings will remove axial play in the main bearing as force is transferred from the nose bearing into the spacer and into the main bearing through the spacer. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.